The present invention relates to a method of pelletizing a compound semiconductor wafer into pellets, and more particularly to a method of dividing a compound semiconductor wafer into pellets by utilizing extremely narrow scribe regions.
FIG. 1 is a plan view illustrative of a compound semiconductor wafer with an orientation flat, wherein scribe lines have been drawn on a surface of the compound semiconductor wafer. The descriptions will be made of the conventional method of dividing the compound semiconductor wafer 1 into a plurality of square-shaped pellets 2 defined by both first scribe regions 3 which extend in parallel to each other over the compound semiconductor wafer 1 in a first direction or horizontal direction parallel to the orientation flat, and second scribe regions 3 which extend in parallel to each other over the semiconductor wafer 1 in a second direction perpendicular to the first direction. FIG. 2 is a fragmentary enlarged plan view illustrative of scribe regions and pellet regions in a compound semiconductor wafer. FIG. 3 is a view illustrative of a dicing method as a conventional method of dividing a semiconductor wafer into pellets, wherein the scratches are drawn by a grinding machine along the scribe regions of the wafer. FIG. 4 is a view illustrative of a point-scribe method as a conventional method of dividing a semiconductor wafer into pellets, wherein a needle is used to draw the scratches along the scribe regions of the wafer.
The above described conventional dicing and point-scribe methods are to draw the scratches by mechanical tools such as a grinder and needle, for which reason surfaces of the scratches are made rough by mechanical shock applied by the mechanical tools such as a grinder and needle. This roughness of the surfaces of the scratches may cause the appearance of cracks and breaking of the pellet regions during the process for cleaving the wafer along the scratches to divide the wafer into the pellets. Once any crack or break appears on the pellets, then those pellets are no longer available as semiconductor chips, whereby the yield is lowered.
The above conventional dicing method and the point-scribe method are engaged with difficulty to further improve the accuracy in position of the grinder or the needle, for which reason it is difficult to further reduce a width of the scribe region in consideration of the necessary margin. This provides a limitation to further improve the required yield.
In the above circumstances, it had been required to develop a novel method of dividing a wafer into pellets with allowing reduction in the necessary width of the scribe region for reducing the total area of the scribe region to improve the yield without, however, causing crack or break of the pellets upon the cleaving process.